1. CFX-10 Introduction
Lecture 1

2. CFX-10 Introduction Main Steps in CFD Analysis Geometry Meshing
Physics Definition
Solver
Post-processing

3. Main Steps in CFD Analysis
Step 1: Geometry DesignModeler or Import from CAD
create a solid representing the fluid flow region
Step 2: Meshing CFX-Mesh, CFX-TurboGrid or ICEM
create a volume mesh using the solid
Step 3: Physics Definition CFX-Pre
define physical models, material properties and boundary conditions
Step 4: Solver CFX-Solver Manager
solve equations and produce a solution
Step 5: Post-processing CFX-Post
analyze and visualize the solver results

4. Step 1: Geometry
DesignModeler or CAD

5. Geometry Create or Import the geometry
Domain in which the governing equations will be solved and solution obtained
ANSYS DesignModeler can be used to create geometry
Results in one or more bodies
Not required if the mesh is imported from a separate application

6. CFX-Mesh, ICEM or CFX-TurboGrid
Step 2: Meshing
CFX-Mesh, ICEM or CFX-TurboGrid

7. Meshing Mesh Generation
Process of generating finite volumes or elements
CFX can accept meshes with elements that are hexahedral, tetrahedral, prismatic (wedges), pyramids or any combination
Surface mesh and volume mesh make up the mesh
Meshes can be created in a different session or imported from another meshing utility

8. Step 3: Physics Definition
CFX-Pre

9. Import Mesh into CFX-Pre
The mesh defines the fluid domain(s) to be solved
Mesh Tab imports and manages grids
Each imported mesh is stored as a Mesh Assembly
Import Mesh
Transform Mesh Assembly
Delete Mesh Assembly
Edit Render Options for Selected Regions
View Mesh Statistics for Selected Regions

10. Create Toolbar
To define your simulation, follow the toolbar from left to right
Some items are optional, depending on your simulation
Hold the mouse over each icon to see what it does

11. Create Toolbar
In the simplest cases, the following items are required after importing the mesh
1. Domains
3. Solver Control
2. Boundary Conditions
4. Write Solve File

12. Create Toolbar
Create a Coordinate Frame – if the default coordinate frame is not sufficient
Define the Simulation Type – steady state (default) or transient
Create a Domain – define properties of fluid, solid and/or porous domain(s)
Create a Subdomain – if you need to apply sources within a domain
Create a Source Point – if you need to apply a point source within a domain
Create a Boundary Condition – define what’s happening at the boundaries
Create a Domain Interface – for periodicity and to connect multiple domains
Define the Global Initial Conditions – initial conditions for all domains
Define the Mesh Adaption Criteria – to adapt the mesh as the solution progresses
Define the Solver Control Criteria – the parameters that control the Solver
Output Control and Monitor Points – the files the Solver outputs
Write Solver File – write a file and proceed to the Solver

13. Domains Define the regions in which the equations are solved
Fluid, solid and porous regions
Pick the fluid(s) or solid materials
Select the physical models:
Turbulence and Heat Transfer model
Buoyancy
Multiphase models
Combustion and Radiation models
Particle Tracking ……

14. Boundary Conditions
Boundary Conditions are needed to completely specify (or close) the problem
Required on all external surfaces of geometry
Boundary values can be constants or CEL expressions
A Default Boundary Condition is applied to external surfaces which have not been explicitly defined
created automatically for each domain
All mesh regions are available in CFX-Post, not just Boundary Conditions

15. Boundary Conditions There are 5 general types of boundary conditions
INLET: allow flow into the domain only
OUTLET: allow flow out of the domain only
OPENING: allow flow in and out of the domain
WALL: no flow, normal velocity is zero
SYMMETRY: flat surface specifying plane of symmetry

16. Solver Control
Control of the CFX-5 Solver is undertaken by the use of Solver Parameters, set on the Solver Control form
Convergence Control
maximum number of iterations
timescale selection
Advection Scheme
Convergence criteria
MAX or RMS residual
conservation target

17. Write Solver File
CFX-Pre writes out a “Definition” (.def) file to run in the Solver
Contains everything needed (mesh and physics) to run the simulation.
CFX-Pre stores mesh data in the “Geometry, Topology and Mesh” (.gtm) file and physics in the .cfx file
Keep these files to re-open simulations in CFX-Pre

18. Step 4: Solver
CFX-Solver Manager

19. Solver Solve the governing equations Set the flow solver options
Iteratively solve the governing equations as a batch process
Obtain convergence

20. Solver Manager The Solver Manager is primarily used to:
start a new calculation, or set up multiple runs
restart a calculation from an earlier solution
examine the problem information
set up parallel runs
monitor residuals, global balances, monitor points, expressions, etc.

21. Step 5: Post-processing
CFX-Post

22. CFX-Post
Examine results, either in graphical or numerical format

23. CFX-Post Provides capability to quantify and visualize results
Typical Post functionality involves
creating Locator Objects (Points, Lines, Slice Planes, etc.)
plotting Visualization Objects (Contours, Vectors, etc.) on locators
evaluating expressions on locators
exporting data for further external analysis
CFX-Post also includes turbomachinery specific post-processing tools

24. CFX-Post: Visualization

25. Main File Types in CFX CFX-Pre CFX-Solver CFX-Post
CFX-Pre case (.cfx) & GTM (.gtm) file CFX Results File (.res) CFX Definition File (.def) Other mesh files
CFX-Pre
CFX-Pre case (.cfx) & GTM (.gtm) file
CFX Definition File (.def)
CFX-Solver
CFX Solver Output file (.out)
CFX Results File (.res)
CFX Definition File (.def) CFX GTM File (.gtm)
CFX-Post

26. Practical Sessions Practical 1: Duct Bend
A simple example to take you through the stages of setting up and running a model and then visualising the results
Practical 2: Duct Bend With Vanes
Include heat transfer and turning vanes (thin surfaces) in the above example.